Issue #14154: Reimplement the bigmem test memory watchdog as a subprocess.

Lib/test/memory_watchdog.py

@@ -0,0 +1,28 @@
+"""Memory watchdog: periodically read the memory usage of the main test process
+and print it out, until terminated."""
+# stdin should refer to the process' /proc/<PID>/statm: we don't pass the
+# process' PID to avoid a race condition in case of - unlikely - PID recycling.
+# If the process crashes, reading from the /proc entry will fail with ESRCH.
+
+
+import os
+import sys
+import time
+
+
+try:
+    page_size = os.sysconf('SC_PAGESIZE')
+except (ValueError, AttributeError):
+    try:
+        page_size = os.sysconf('SC_PAGE_SIZE')
+    except (ValueError, AttributeError):
+        page_size = 4096
+
+while True:
+    sys.stdin.seek(0)
+    statm = sys.stdin.read()
+    data = int(statm.split()[5])
+    sys.stdout.write(" ... process data size: {data:.1f}G\n"
+                     .format(data=data * page_size / (1024 ** 3)))
+    sys.stdout.flush()
+    time.sleep(1)